Method of making metal castings



Jan. 18, 1927. 1 614,846

W. D. MOORE METHOD OF MAKING METAL CASTINGS Filed May 29, 1925 INVENTOR 41 1 /mwfl M0055 Patented 18, 1927.

PATENT OFFICE.

WILLIAM I). MOORE, OF BIRMINGHAM, ALABAMA, ASSIGNOB TO SAND SPUN PATENTS CORPORATION, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

UNITED STATES METHOD OF MAKING METAL CASTINGS.

Application filed May 29, 1925. Serial No. 38,704.

This invention is an improvement in methods of making metal castings, and more particularly in methods of making hollow castings, such as cast iron pipe, in refractory molds.

Such castings are made by introducing molten metal into a refractory mold, supported for rotary movement, and preferably supported for tilting movement, and with the mold inclined during the pouring operation, The mold is rotated while the metal is poured, and in the latter instance it is restored to horizontal position either during the pouring or immediately thereafter. That is an additional movement, other than rotary, is imparted to the mold, thereby to modify the circumferential direction of flow of the metal to evenly distribute the same upon the interior of the mold.

The castings obtained by centrifugal operation with green sand molds, have desirable properties not obtaining in their entirety in either ordinary sand cast metal, or in centrifugal cast products. Such castings, that is castings made centrifugally in green sand molds combine the superior resistance to corrosion and other disintegrating reactions, characteristic of sand cast metal, with the great density, solidity and strength of centril'ugally made cast ngs.

The molds used have heretofore been of metal or'of a refractory material such as sand, and with refractory material of every character, the molds have heretofore either been baked in the attempt to eliminate from the sand all the moisture possible, or if not baked they have been faced with a protective facing, as for instance cement, in the manner described in Patent-No. 1,471,052, filed Oct. 1.6, 1923.

The baking and the protective facing are designed to serve somewhat similar functions, among others to prevent cutting and washing of the sand by the molten metal as it flows into the mold; the tendency to the formation of scruff and defects of the pocket or honcycmnb type; and instability of the sand lining when sub'ected to high speeds of rotation; all of which are problems to be solved in centrifugal casting.

The object sought by baking is to make the mold bone-dry or substantially so, thus to remove the moisture which is recognized as the cause of blow holes, gas pockets, segregations of various kinds and the like. The operation is relatively expensive, requiring additional labor, fuel, and time, usually from 6 to 12 hours.

The protective facing may be of the character specified in the above mentioned patent, as for instance a natural cement such as pulverized calcined argillaceous limestone. This is a refractory non-combustible material, capable of fusing with the metal of the casting, and it provides a shell like coating white or grayish white in appearance, and to that extent a departure from the accepted type,

For the reasons above mentioned, as well as .to reduce the cost of the operation, and to obtain a more desirable color, and a better finishof the product, it is desirable to produce castings centrifugally in green sand molds, and I have discovered that hollow articles, such as pipe, may be cast in unbaked or wet sand :molds, without the blowing back of gases, such as would cause blisters, boils and the like, there being sufficient ferro-slatic pressure to drive the gases through the mold wall.

Some character of facing is however desirable to provide a suitable finish for the product, and I have discovered that a suitable material for this purpose is the facing of wet blacking ordinarily used for dry sand work. This facing has for its base a finely comminuted or powdered carboniferous material, and it is applied in a water emulsion. \Vhen applied a thick sus ension of facing material is left on the mol face.

This facing of suspended carboniferous matter, while combustible in oxygen is not consumed during the casting operation, because of the lack of oxygen, nor does it fuse with the metal of the casting. It remains unchanged, except for loss of moisture content. If the casting is permitted to cool before removal from the mold, the calbo naceous matter will form in a layer which separates easily from the casting, leaving the casting face of a desirable natural dark gray color.

If however the casting should be removed from the mold while it is still hot, that is while the temperature is sufficiently high to ignite the carboniferous facing material in the presence of oxygen, the facing will be consumed, leaving the casting face of a color much lighter than when the facing is removed mechanically after cooling.

In order to protect those parts of the mold which are subjected to the most violent action of the molten metal during the casting operation, from any possible cutting or washing action, the moisture content of the mold surface over zones which are liable to this action may be subjected to the drying action of a flame for a few minutes only, immediately preceding the casting operation.

While I do not wish to restrict the scope of the invention by any unwarranted assumptions, as to the exact action that takes place, I am of the opinion that the mold is first skin dried in effect by fleeting contacts of the inner wall thereof with the molten metal, before the mold wall is completely covered with a layer of molten metal, which might impede the free venting ofthe vapor first generated, or which might be effected by such vapor to produce blow holes, blisters and the like. a

During the pouring of the mold the speed of rotation of the mold is not so rapid that the centrifugal force-will hold the molten metal in contact with the mold wall throughout. The metal is carried only, to the high est point of the mold, from whence it falls back into the pool of molten metal. Before the centrifugal force is sufiicient to hold the metal in contact with the mold wall'throughout its travel, the facing and a thin la er of the mold wall immediately behind the acing is-dry and at a high temperature.

The highest temperature is at theinner face of the mold, and the temperature of-the mold wall increases from this face to the outer face. The moisture is subjected to alternate vaporization and condensation as it travels toward the outer wall in a manner to influence its travel in that direction, and it finds its way to the exterior to the mold, and to the vents of the flask without disturbing the inner surface of the mold wall.

That portion first vaporized by the molten metal is condenseds or absorbed by the wet sand immediately outside of the same, to be again vaporized and recondensed as the temerature rises from within outward. I have n led to these conclusions by the discovery that better results areobtained with the use 'of an open grained sand, that is a sand relatively free from bending material, other than water. S

Centrifugally casting in a wet sand.

mold with a wet facing is a radical departure from accepted practice, and so far as I' am aware, I am the first in the art to so cast, and while the invention will be described in detail, such description is intended as only one examplification of the method, it being understood that various changes may vbe made without departing from the spirit of the invention as defined in the claims appended hereto. I

In the drawings is shown a longitudinal section of a mold prepared in accordance with the method, and ready for casting.

In carrying out the improved method, a sand mold is prepared in the usual way, from sand which may be that commonly used, or combined with other materials, in accordance with the ends sought, and when completed the interior of the mold is faced with a water emulsion of non-soluble carboniferous material, such as finely divided anthracite coal, nut coke, or both, modified by other constituents if desired.

This facing which is usually of about the consistency of muddy water, is applied to the mold in any usual or desired manner. The facing surfaces the mold, and prevents the molten metal from fusing with the sand. Although combustible in the usual meaning of the word, it is not efl'ected during the casting operation, and when the casting is cooled, it is substantially unchanged, except as to moisture content. It is easily separated from the casting, leaving a natural dark gray colored surface.

In some instances, it may be advisable to subject the mold to the action of a flame for a period ofapproximately five minutes, just prior to the casting operation. This treatment reduces the moisture content of the facing and the sand in zoneswhich are subject to the most severe action of the flowing metal, before the rapid rotation of the mold is initiated. The sand and facing ir such zones is almost if not completely dry, and the sand and facing in the zones immediately adjacent the first named zones which are also subject to severe action of the molten metal, but to less degree than the first named zones, have the moisture content ma terially reduced.

Referring to the drawings, in which the moisture content of the sand constituting the mold A in the flask B is indicated, it will be noted that before treatment with the flame, the moisture content of the sand is about 11%. The zones C at the ends of the mold which will be subjected to the most severe action of the molten metal during the casting operation have' the moisture content reduced to about 1%, and in adjacent zones D which are subject to a less violent action, the moisture content is reduced to about 5%.

So prepared the molds are ready for castthe mold is inclined or tilted from the horizontal being shown and described in the above mentioned patent. lVith this construction, the mold is restored to the horizontal, at the commencement of the pouring operation, or immediately after, thereby to uniformly distribute the molten metal over the mold surface.

When the molten metal is poured into the mold, it strikes the zone C at the spigot end of the pipe, and this zone when the pipe is treated with the gas flame as above specified 1s almost dry, the moisture content being approximately 1%. The metal then flows over the zone D Which is partially dry, and from thence to the bell end of the pipe. The most severe action of the molten metal at the bell end is at the zone C, where the direction of flow changes, and where the speed of the flow is increased to some extent. This zone corresponds to the dry zone at the spigot end, and it will be evident that at the points where the action of the molten metal is most severe it does not come directly into contact with the sand and facing having the highest moisture content.

The moisture content of the sand is slightly increased by the application of the wet facing and the following table shows the approximate moisture content of cross-sections at the different stages and different localities noted:

, Per Cent. 1st original sand 10. 5 2nd after blacking 11.2 3rd ready to castbead 7.8 4th ready to castmiddle 11. 1 5th ready to cast-bell 8.6

The sand used as previously stated is the regular heap sand, with or without the addition of other matter. The wet facing is composed primaril of carbon, which may be obtained by pu verizing nut coke to the fineness of flour and mixing with water and a suitable binder, as for instance clay. After proper soaking and seasoning, the mixture is brought toa fluid state of such nature as will best suit the sand to be coated or faced.

A suitable sand mixture is that specified in the above mentioned patent, which is composed of silica sand, sharp sand, and molding sands mixed in the proportions -of about 50% of the first, 35% of the second, and 15% of the third, although other mixtures may be em loyed.

The liquid facing may be water emulsion of any of the composition facings used in standard foundry practice. All of these facings have acarbomferous material as a base, anthracite coal, plumbago, nut coke or the like, the carboniferous material being finely pulverized, and used by mixing with water, to which may or may not be added a binder, as may be desired, or found suitable in a particular case. The carbon makes up usually of the total solids, and the primary purpose of such material is to form a protective coating on sand surfaces, so that the hot metal will not fuse with the sand.

In the usual foundry practice the mold when prepared, and regardless of the method of preparation or the nature of the sand, is submitted to a drying operation in which an attempt is made to bring the mold into a bone-dry condition. In the prior patcut above mentioned, wet or unbaked sand molds were used with a protective coating which would fuse with the metal, in accordance with vthe method set forth in application Serial Number 30,609, filed May 15, 1925, becoming a part of the pipe. In the present invention wet or unbaked sand molds are used, faced with a wet carboniferous material which will remain substantially unchanged during the casting operation except for moisture content, and which will not fuse with the metal of the casting.

The distinctive feature of the present invention is the use of a wet, green or unbaked sand mold, faced with a wet facing which will remain substantially unchanged during the casting operation. A facin which will not fuse with the metal, and which will flake easil from the casting, after cooling leaving it of the natural color, and in condition to be treated with a coating of an desired character, such as cement, aspha t, or the like. In the prior patent above mentioned, the facing is of a material refractory and non-combustible, but fusing with and becomin a part of the product.

The mold may be prepared as described in the said patent or in an other suitable manner, with only such mo ifications in the normal moisture content, as are desired to resist the most violent effects of the molten metal during the inflow thereof into the mold. The invention also contemplates casting in baked refractory molds, with a wet facing, of the character above specified.

I claim:

1. The method of centrifugally casting hollow metal bodies, which comprises charging molten metal into a rotary wet faced green or unbaked sand mold.

2. The method of centrifugally casting hollow metal bodies, which comprises charging molten metal into a rotary wet faced greenor unbaked sand mold, having zones of reduced moisture content near its-ends.

3. The method of centrifugally casting hollow metal bodies, which comprises charging molten metal into a rotary green or unbaked sand mold provided, with a protective facing of a non-fusible solid.

4. The method of centrifugally casting 5. The method of centrifugally casting hollow metal bodies, which comprises charging molten metal into a rotary green or unbaked sand mold provided with a protective facing of a finely pulverized nonfusible solid, and having zones of reduced moisture content near its ends.

6. The method of centri'fugally casting hollow metal bodies, which comprises charging molten metal into a rotary green or unbaked sand mold provided with a protectivefacing of a finely pulverized nonfusible solid a )plied in emulsion.

7. The met 0d of centrifugally casting hollow metal bodies, which comprises charging molten metal into a rotary green or unbaked sand mold provided with a wet facing of a finely pulverized non-fusible solid.

8. The method of centrifugally casting hollow metal bodies, which comprises charging molten metal into a rotary green or unbaked sand mold provided with a wet facing of a finely pulverized solid.

9. The method of centrifugally casting hollow metal bodies, which comprises charging molten metal into a rotary green or unbaked sand mold'provided with a wet facing of a finely pulverized solid, and having zones of reduced moisture content near its ends.

10. The method of centrifugally casting hollowmetal bodies which consists in pouring molten metal into a rotary green sand mold with a non-soluble non-fusible facing, while the mold is in a position inclined to the horizontal, and moving the mold to a substantially horizontal position while the metal is still in a fluid condition.

11. The method of centrifugally casting hollow metal bodies, which consists in pouring molten metal into a rotary inclined green or unbaked sand mold, having a protective facing of non-soluble non-fusible material, and moving the mold to a substantially horizontal position while the metal is still in a fin id condition. A

12. The method of centrifugally casting .hollow metal bodies, which consists in pour ing molten metal into a rotary inclined green or unbaked sand mold provided with a protective facing of non-soluble non-fusible material in emulsion, and with the moisture content thereof lessened over zones subject to the most violent action of the metal, and moving the mold to a substantially horizontal position while the metal is still in a fluid condition.

13. The method of centrifugally casting hollow metal bodies, which consists in pouring molten metal into a rotary inclined green or unbaked sand mold rovided'with a protective facing of nonusible material, and having the moisture content thereof lessened over zones near the ends of the mold, and

moving the mold to substantially horizontal position while the metal is still in a fluld condition. i

14. The method of centrifugally casting hollow metal bodies with bell ends, which consists in inclining, with the bell end downward, a rotary green or unbaked sand mold having a non-soluble non-fusible protective facing, pouring molten metal toward the said end, and moving the mold to a substantially horizontal position while the metal is still in a fluid condition.

15. The method of centrifugally casting hollow metal bodies with bell ends, which consists in inclining, with the bell end downward, a rotary green or unbaked sand mold,

rovided with a protective non-soluble nonusible material in emulsion, and leveling the mold while the metal is still in a fluid condition.

16. The method of centrifugally casting hollow metal bodies with bell ends, which consists in inclining, with the bell end downward a rotary green or unbaked sand mold provided with a protective facing of a water emulsion of pulverulent non-soluble material and having-the moisture content thereof reduced over zones subject to the most violent action of the molten metal, and rapidly and gently leveling the mold while the metal is still fluid.

17. The method of centrifugally casting hollow metal bodies, which consists in inel ning a rotary green sand mold, provided with a protective facing of an emulsion of non-soluble non-fusible material, and skin dried near the ends over zones subject to the most violent action of the molten metal, and quickly leveling the mold while the metal is still fluid.

18. The method of centrifugally casting hollow metal bodies with bell ends, which consists in preparing a green sand mold provided with a protective facing of an emulsion of a non-soluble-non-fusible material,

skin drying the ends of the mold over zones subject tov the most violent action of the molten metal, inclining the mold with the bell end downward, imparting rotation to the mold, and pouring and leveling while ghedmold is rotating and the metal is still hollow metal bodies, which consists in pourmg molten metal into an inclined rotary mold'of refractory material, provided with 19. The method of centrifugally casting. I

sand mold faced with an emulsion of a nonfusible solid, and moving the mold bodily in a direction to impart to the metal while it is still in a fluid condition a flow longitudinally of the mold.

21. The method of centrifugally casting hollow metal bodies, which consists in pouring molten metal into an inclined rotary green sand mold faced with a non-fusible solid and quickly' leveling the mold while the metal is still in a fluid condition.

22. The method of centrifugally castin hollow metal bodies having bell ends, whic consists in pouring molten metal into a rotary-green sand mold faced with anonfusible solid and arranged with the bell end at a lower level thanthe spigot end, and

bodily moving the mold in a direction to im art to the metal while it is'still in a fluid condition a flow longitudinally of the mold.

23. The method of centrifugally casting hollow metal bodies which consists in pouring molten metal into an inclined rotary green sand .mold faced with a water emulsion of a non-fusible solid having a high content of carbon, and quickly leveling the mold while the metal is still in a fluid condition.

24. The method of centrifugally casting hollow metal bodies, which consists in pouring molten metal into a rotary mold of refracto material, faced with-a mixture of a nonusible solid and water.

25. The method of centrifugally casting hollow metal bodies, which comprises chargmg. molten metal into a wet faced green or unbaked sand mold while it is rotating at a speed insuflicient to ,hold the molten metal on the mold wall, and abruptly increasing the speed of rotation at ornear the end of the charging to apply the metal to the wall and retain it thereon.

26. The method of, centrifugally casting hollow metal bodies, which comprises'chargtive facing of a non-fusible solid, while it is rotating at a speed insufiicient to hold the molten metal on the mold wall, and abruptly increasing the s eed of rotation at or near the end of the c arging to apply themetal to the wall and retain it thereon.

28. The method of centrifugally casting hollow metal bodies, which comprises charging molten metal into a wet faced green or unbaked sand mold provided with a protective facing of a finely pulverized non-fusible solid in emulsion While it is rotating at a speed insufiicient to hold the molten metal on the mold wall, and abruptly increasing the speed of rotation at or near. the end of the charging to apply the metal to the wall and retain it thereon.

29. The method of centrifugally casting hollow metal bodies, which comprises charging molten metal into an incliiied wet faced green sand mold while it is rotating at a" speed insufiicient to retain the metal on the mold wall, and while the mold is moving into horizontal position, and abruptly increasing the speed when the mold is near d in horizontal position to apply the metal to the mold wall.

Signed at Birmingham in the county of Jefferson and State of Alabama this 1st day of April, A. D. 1925.

WILLIAM D. MOORE. 

